package binaryTree;

import java.util.LinkedList;
import java.util.Queue;

/**
 * Created with IntelliJ IDEA.
 * Description: 实现二叉树的基本操作
 * User: 王圆豪
 * Date: 2024-08-26
 * Time: 23:58
 */
public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }

    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode treeNode1 = new TreeNode('A');
        TreeNode treeNode2 = new TreeNode('B');
        TreeNode treeNode3 = new TreeNode('C');
        TreeNode treeNode4 = new TreeNode('D');
        TreeNode treeNode5 = new TreeNode('E');
        TreeNode treeNode6 = new TreeNode('F');
        TreeNode treeNode7 = new TreeNode('G');
        TreeNode treeNode8 = new TreeNode('H');
        treeNode1.left = treeNode2;
        treeNode1.right = treeNode3;
        treeNode2.left = treeNode4;
        treeNode2.right = treeNode5;
        treeNode4.left = treeNode8;
        treeNode3.left = treeNode6;
        treeNode3.right = treeNode7;
        return treeNode1;
    }


    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) return;
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) return;
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if (root == null) return;
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) return 0;
        return size2(root.left) + size2(root.right) + 1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if (root == null) return;
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) return 0;
        if (root.left == null && root.right == null) {
            return 1;
        }
        int l = getLeafNodeCount2(root.left);
        int r = getLeafNodeCount2(root.right);
        return l + r;
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null) return 0;
        if (k == 1) {
            return 1;
        }else {
            return getKLevelNodeCount(root.left, k - 1) + getKLevelNodeCount(root.right, k - 1);
        }
    }


    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) return 0;
        int l = getHeight(root.left);
        int r = getHeight(root.right);
        return l > r ? l + 1 : r + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) return null;
        if (root.val == val) {
            return root;
        }
        if (find(root.left, val) != null) {
            return root.left;
        }
        if (find(root.right, val) != null) {
            return root.right;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null) return;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if (cur.left != null) queue.offer(cur.left);
            if (cur.right != null) queue.offer(cur.right);
            System.out.print(cur.val + " ");
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null) return true;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        TreeNode cur = root;
        while (cur != null) {
            queue.offer(cur.left);
            queue.offer(cur.right);
            cur = queue.poll();
        }
        return isAllNull(queue);
    }

    boolean isAllNull(Queue<TreeNode> queue) {
        while (!queue.isEmpty()) {
            if (queue.poll() != null) {
                return false;
            }
        }
        return true;
    }
}
